运行环境的开放性和动态性使得Web服务QoS具有内在的不确定性。为此,首先对QoS不确定性进行了分析,并分别采用实数、区间数和随机数对不同特性的Web服务QoS进行描述。然后,结合用户QoS需求约束,分别利用可能度和半方差理论实现区间数和...运行环境的开放性和动态性使得Web服务QoS具有内在的不确定性。为此,首先对QoS不确定性进行了分析,并分别采用实数、区间数和随机数对不同特性的Web服务QoS进行描述。然后,结合用户QoS需求约束,分别利用可能度和半方差理论实现区间数和随机变量的比较,将不确定混合QoS感知的服务选择问题转化为确定型多属性决策问题,并利用TOPSIS(technique fororder preference by similarity to ideal solution)方法进行求解。服务选择考虑了客观权重和主观权重。最后,通过实验验证了服务模型的有效性。展开更多
Ethereum blockchain is a new internetware with tens of millions of smart contracts running on it.Different from general programs,smart contracts are decentralized,tamper-resistant and permanently running.Moreover,to a...Ethereum blockchain is a new internetware with tens of millions of smart contracts running on it.Different from general programs,smart contracts are decentralized,tamper-resistant and permanently running.Moreover,to avoid resource abuse,Ethereum charges users for deploying and invoking smart contracts according to the size of contract and the operations executed by contracts.It is necessary to optimize smart contracts to save money.However,since developers are not familiar with the operating environment of smart contracts(i.e.,Ethereum virtual machine)or do not pay attention to resource consumption during development,there are many optimization opportunities for smart contracts.To fill this gap,this paper defines six gas-inefficient patterns from more than 25,000 posts and proposes an optimization approach at the source code level to let users know clearly where the contract is optimized.To evaluate the prevalence and economic benefits of gas-inefficient patterns,this paper conducts an empirical study on more than 160,000 real smart contracts.The promising experimental results demonstrate that 52.75%of contracts contain at least one gas-inefficient pattern proposed in this paper.If these patterns are removed from the contract,at least 0.30 can be saved per contract.展开更多
文摘运行环境的开放性和动态性使得Web服务QoS具有内在的不确定性。为此,首先对QoS不确定性进行了分析,并分别采用实数、区间数和随机数对不同特性的Web服务QoS进行描述。然后,结合用户QoS需求约束,分别利用可能度和半方差理论实现区间数和随机变量的比较,将不确定混合QoS感知的服务选择问题转化为确定型多属性决策问题,并利用TOPSIS(technique fororder preference by similarity to ideal solution)方法进行求解。服务选择考虑了客观权重和主观权重。最后,通过实验验证了服务模型的有效性。
基金supported by the Key-Area Research and Development Program of Guangdong Province of China under Grant No.2020B010164002the National Natural Science Foundation of China under Grant No.62032025.
文摘Ethereum blockchain is a new internetware with tens of millions of smart contracts running on it.Different from general programs,smart contracts are decentralized,tamper-resistant and permanently running.Moreover,to avoid resource abuse,Ethereum charges users for deploying and invoking smart contracts according to the size of contract and the operations executed by contracts.It is necessary to optimize smart contracts to save money.However,since developers are not familiar with the operating environment of smart contracts(i.e.,Ethereum virtual machine)or do not pay attention to resource consumption during development,there are many optimization opportunities for smart contracts.To fill this gap,this paper defines six gas-inefficient patterns from more than 25,000 posts and proposes an optimization approach at the source code level to let users know clearly where the contract is optimized.To evaluate the prevalence and economic benefits of gas-inefficient patterns,this paper conducts an empirical study on more than 160,000 real smart contracts.The promising experimental results demonstrate that 52.75%of contracts contain at least one gas-inefficient pattern proposed in this paper.If these patterns are removed from the contract,at least 0.30 can be saved per contract.
